The present invention is generally directed to toner processes, and more specifically, to chemical in situ processes which comprises the aggregation and fusion of latex, colorant, and optional additive particles into toner particles, and wherein there is selected a latex containing a dimeric component, an oligomeric component, or mixtures thereof. More specifically, the present invention relates to toners and processes thereof wherein there is selected for the latex a dimeric acrylic acid, an oligomeric acrylic acid, or mixtures thereof, and yet more specifically, a dimeric acrylic acid containing carboxylic acid groups, or an oligomeric acrylic acid containing carboxylic acid groups. The toner compositions resulting possess, for example, a volume average diameter of from about 1 to about 25 microns, and preferably from about 3 to about 10 microns in volume average diameter, with a narrow particle size distribution as conventionally characterized by GSD of, for example, less than 1.35, and preferably less than about 1.25, and more specifically, from about 1.12 to about 1.25 as measured on the Coulter Counter, and which toners can enable improved image fusing, that is for example, fusing of the image can be accomplished at a low temperature, for example, with a toner Minimum Fix Temperature (MFT) of from about 150.degree. C. to about 170.degree. C., as compared to toners prepared ) from latexes with monomeric acrylic acid, which toners possess a MFT of from about 180.degree. C. to about 200.degree. C., and wherein the invention toners possess excellent triboelectrical charging characteristics with a toner tribo of from about 20 .mu.C/gram to about 40 .mu.C/gram (microcoulombs per gram) at 50 percent relative humidity, as compared, for example, to toners prepared from latexes with monomeric acrylic acid that possess in a number of instances a low toner tribo of from about 10 .mu.C/gram to about 15 .mu.C/gram at 50 percent relative humidity; and acceptable gloss, for example with a gloss of from 20 GSU (Gardner Gloss Units) up to 70 GCU as measured by Gardner Gloss meter matching of the toner and paper after fixing the toner to paper substrates. The resulting toners can be selected for known electrophotographic imaging and printing processes, including digital color processes.
The dimers and oligomers selected, which are available from a number of sources, can be considered alkenoic acids, that is for example, olefinically unsaturated carboxy functional monomers of, for example, alpha, beta-ethylenically unsaturated carboxylic acids, preferably of the formula ##STR1## wherein n is a number of from about 1 to about 20, and preferably from about 1 to about 13, and more preferably of from 1 to about 5; (about, and between include all values therebetween throughout). These acids can be prepared conveniently by the Michael addition reaction of acrylic acid with itself, the degree of addition primarily determining the value of n. The acid molecule where n equals to 1 is also known as diacrylic acid, .beta.-acryloxypropionic acid, or .beta.-carboxyethyl acrylate of the formula ##STR2##
The degree of polymerization is conveniently characterized by the average value n, thus for example samples of the oligomer, or dimer will normally have a low degree of polymerization, and wherein the oligomers, are, for example, comprised of mixtures of individual molecules with the formulas illustrated herein. For an individual molecule, such as dimer, trimer, tetramer, or higher mers, n is preferably an integer or number of, for example, about 2 to about 20. The oligomer acrylic possesses, for example, an n value of from about 2 to about 20, and preferably from about 2 to about 13, and more preferably from 2 to about 5, and the M.sub.w weight average molecular weight, of the oligomer acrylic acid is, for example, from about 200 to about 3,500, and preferably from about 200 to about 2,500, and the M.sub.n thereof is, for example, preferably from about 200 to about 1,500, and more preferably from about 200 to about 1,000, as determined by Gel Permeation Chromatography. The dimer can be considered as being the reaction product of two acrylic acid monomers, and wherein n is preferably equal to 1. The molecular weight for a dimer is, for example, about (the dimer is a believed to be the reaction product of two acrylic acid monomers, and no mixture is present) 144 grams/mole.
Acryloxypropionic acid and higher oligomeric homologues, which higher is, for example, a M.sub.w of from about 200 to about 3,500, can be prepared by any of a variety of methods including (1) the addition of acrylic acid to .beta.-propiolactone; (2) the reaction of acrylic acid or acryloyl chloride with 3-hydroxypropionic acid, or the (3) thermal dimerization/oligomerization of acrylic acid either with or without added catalysts. For example, .beta.-acryloxypropionic acid can be prepared by the dimerization of acrylic acid by the known Michael addition reaction promoted by triphenylphosphine. The dimerization in bulk acrylic acid results from the electrophilic addition of one acrylic acid molecule across the vinyl bond of a second acrylic acid to form an ester group. .beta.-acryloxypropionic acid can also be generated by heating acrylic acid at about 150.degree. C. to about 160.degree. C. in the presence of a catalytic amount of aluminum trichloride. .beta.-Acryloxypropionic acid molecules can undergo subsequent Michael additions with other acrylic acid molecules to form higher molecular-weight oligomers, which possess an M.sub.w of from about 200 to about 3,500. Also, .beta.-acryloxypropionic acid is preferably admixed in varying proportions with the higher oligomeric homologues. The acid(s) selected are usually of commercial grade and therefore contain small quantities of acrylic acid of from about 5 to about 20 weight percent.